Scientists at the International Agency for Research on Cancer (IARC), the UK Medical Research Council and Cancer Research UK announced today the publication in the Lancet of two articles reporting strong scientific evidence linking high fibre diet with a reduced incidence of both cancer and pre-cancerous polyps of the colon and rectum. For reference, colon and rectal cancers rank among the most common cancers worldwide, with almost 1 million new cases every year. These tumours are most prevalent in the economically developed world but their incidence is increasing in developing countries as well. Incidence of colon cancer is fairly similar in men and women while cancer of the rectum is more frequent in men than in women.
Dr Elio Riboli, Chief of the Nutrition and Cancer Unit at IARC, coordinates the EPIC study, which he describes as a large multidisciplinary project designed to investigate the role of diet, lifestyle, metabolic and genetic characteristics in cancer causation and prevention. The study is based on 522,000 individuals aged 25-70 from 24 study centres in Denmark, France, Germany, Greece, Italy, the Netherlands, Norway, Spain, Sweden and the UK. The EPIC study was initiated ten years ago with the key support of the European Commission Public Health Programme. Many national public institutions and charities have also substantially contributed to the setting up of the project making it an example of European Community added value.
Dr Elio Riboli summed up the main results of this study: «After an average follow-up of 4.5 years, the study could diagnose 1,065 cases of colorectal cancer. Individuals in the top 20% for fibre intake, that is who ate 35 grams of fibre per day on average, saw their risk of colorectal cancer reduced by 40% compared with others consuming 15 grams per day on average. The major breakthrough of this particular study is it shows that it is possible to significantly reduce bowel cancer risk by moderately increasing consumption of whole cereals, fruit and vegetables, which are the main sources of dietary fibre».
Dr Sheila Bingham (Head of Diet and Cancer Group, MRC Dunn Human Nutrition Unit, Cambridge UK) warned, however, that« it is important for people to be aware that fibre supplements or special foods with added fibre were not studied and it should not be assumed that they have the same protective effect as foods that are naturally rich in fibre such as cereals, vegetables and fruits. The people who had the most protection were eating about 7 portions of fruit and vegetables per day, similar to the amounts eaten by Southern Mediterranean populations, and equivalent to 6 slices of wholemeal bread each day, whereas those at most risk were only eating about 2 portions fruit and vegetables per day. »
Professor Nick Day (University of Cambridge) stated that «studying so many different populations with different diets enabled us to get a much more accurate picture of how different kinds of foods contributing fibre to our usual diet relate to the incidence of colorectal cancer.»
«This issue of The Lancet, says Lynnette Ferguson (University of Auckland, New Zealand) in the Editorial, contains two important papers that associate high intake of dietary fibre with a decreased risk of either colonic adenomas or colorectal cancer. »
Indeed, the second study was conducted within the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, a randomized controlled trial designed to evaluate methods for the early detection of cancer. The study compared fibre intake of 33,971 participants who were sigmoidoscopy-negative for polyps, to 3,591 cases with at least one histologically verified adenoma in the distal large bowel (i.e., descending colon, sigmoid colon, or rectum). The study found that high intakes of dietary fibre were associated with a lower risk of colorectal adenoma (non-malignant polyps which are often a precursor of malignant disease). Participants in the top 20% for dietary fibre intake (more than 30 grams per day) had a reduction in risk of adenoma by about _ compared to individuals in the lowest 20% for fibre intake (less than 15 grams per day).
Dr Ulrike Peters, of the NCI, says that: «These two studies (EPIC and PLCO) suggest that it has been premature to dismiss a role for dietary fibre in the prevention of colorectal cancer. »
While the results from both studies did not, and could not address, the effects of changes in dietary patterns on cancer risk, taken together, they provide a strong body of evidence to support cancer prevention campaigns, aimed at advocating for a higher level of dietary fibre intake for all.
1 The Lancet, Volume 361, 3 May, 2003, pp. 1496-1501